Whether you prefer the iPhone, Android, Windows Phone or BlackBerry, it’s hard to deny that Apple‘s phones are the best-looking of the bunch.

For years, it seemed like other phone makers weren’t even trying to compete on design. While competitors kept up with the iPhone in thinness and lightness, they relied almost exclusively on plastic, making their phones feel creaky and cheap.

Lately, phone makers besides Apple have been coming around to the idea of premium designs. The HTC One is a gorgeous phone encased in a single slab of aluminum, and Nokia is reportedly working on an aluminum-clad Windows Phone. Although Samsung is using plastic for the Galaxy S 4, the company is rumored to be using metal for the next Galaxy Note. Aluminum isn’t the only material phone makers are turning to, either; Sony’s Xperia Z and Google’s Nexus 4 have glass panels on both the front and back of the phones — a nod, perhaps, to Apple’s iPhone 4 and 4S.

What took Apple’s rivals so long? I asked Ming-Chi Kuo, an analyst at KGI Securities with solid supply chain sources, to shed some light on the matter. He shared a couple theories for why phone makers are suddenly interested in aluminum, in particular:

Aluminum is now cheaper and easier to implement thanks to Apple itself, and its extensive use of the material in products like the iPhone 5 and iPad. “Apple is the first one to boost the demand for metal casing in the consumer electronics market and it drives the related suppliers of aluminum casing (e.g. equipment providers, casing makers) to invest more on capacity and technology,” Kuo wrote in an e-mail.

High-end phones are facing tougher competition from cheaper ones, and using aluminum is one way for smartphone makers to differentiate their more expensive products. That makes sense to me; the difference between a high-end phone and a cheaper product isn’t as significant as it used to be, leading to the perception that the latest and greatest smartphones are kind of boring. If you’re an Android user, a shiny aluminum design might be the one thing that convinces you to spend a little more.

I have another theory: in the United States, wireless carriers haven’t been futzing with phone makers’ designs like they used to. Whereas each carrier used to demand variants on phones like the Galaxy S, with their own designs, branding and features, carriers like AT&T and Verizon now seem more content to let phone makers come up with a single design, even if it’s not an exclusive. Apple led the way on that front, followed by Samsung, and now HTC is going the same route with the One. It’s easier to mass produce one design than a half-dozen variants, which could mean phone makers are having an easier time using high-end materials.

Plastic does have its defenders: Some users insist that it feels less fragile than glass or metal — but it also makes the phone feel more like a toy than a precision instrument. As Android and Windows Phone become more refined, I’m glad to see some phone makers using high-grade materials to match.

Not that it really matters, because you’ll probably put an ugly case on the thing anyway.